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Relative phase angle between two accelerometers can be computed from the Transfer Function or complex division of Rover-accel. by Reference-accel.. This requires a two-channel analyzer (DAQ) with simultaneous sampling.

The other method is to use a Tachometer (1xSS) as the Reference and compute phase of each accelerometer referenced to the Tachometer Shaft Marker position.

Walt

Last edited by Registered Member
@Registered Member posted:

Relative phase angle between two accelerometers can be computed from the Transfer Function or complex division of Rover-accel. by Reference-accel.. This requires a two-channel analyzer (DAQ) with simultaneous sampling.

The other method is to use a Tachometer (1xSS) as the Reference and compute phase of each accelerometer referenced to the Tachometer Shaft Marker position.

Walt

Hi Walt, Thanks for your explanation.

I have one sensor at each end of shaft which are connected to separate channels in analyzer.I do have tachometer signal but I can't say that I have tracked waveform i.e. synchronized to speed.I am sure on asynchronous waveform data available.

Also those sensors are not placed at same location (o clock positions).

It is not a good idea to try to compensate Phase Angle for two different accelerometer Clock Angle positions beyond about +/- 10-degrees. For an ODS test you can leave the Reference accelerometer at one Measurement Point (location and Angle) typically at highest vibration and move the other accelerometer to other measurement points (Locations and Angles). I prefer to map the motion in each of three planes (typically H, V, A) as necessary. The Rover accelerometer would then be put in the same Location as the Reference accelerometer but oriented for the measurement point of interest (H, V, or A). I also start ODS Test with both accelerometer side-by-side to get a rough calibration of Amplitude (Ratio) and Phase for the Frequency(s) of interest.

Walt

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